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    2. Grade C65500

    ASTM F468/F468M Grade C65500 655 Silicon Bronze Fasteners

    High quality ASTM F468 Silicon Bronze fasteners manufactured for industrial and corrosion resistant applications.

    ASTM F468/F468M Grade C65500 Silicon Bronze fasteners are manufactured in accordance with ASTM specifications for nonferrous bolts, hex cap screws, socket head cap screws, and studs.

    Chemical Requirements

    UNS Designation Number Alloy General Name Al Cu, min Fe,max Mn,max Ni,max P Si Zn, max A Pb,max Tin As,max
    Grade C65500 655 silicon bronze . . . 94.8 D 0.8 1.5 0.6 . . . 2.8-3.8 1.5 0.05 . . . . . .
    • (A) Elements shown as balance shall be arithmetically computed by deducting the sum of the other named elements from 100.
    • (B) Copper plus specified elements = 99.8 min; copper plus silver = 88.5-91.5.
    • (C) Cobalt is to be counted as nickel.
    • (D) Minimum content of copper plus all other elements with specified limits shall be 99.5 %.
    • (E) An alloy containing as high as 2.6 % silicon is acceptable provided the sum of all the elements other than copper, silicon, and iron does not exceed 0.30 %.

    Mechanical Requirements

    Alloy Mechanical Property Marking Nominal Thread Diameter, in. Hardness A Full-Size Tests B Machined Specimen Tests
    Tensile Strength, ksi Yield Strength, min, ksi C Tensile Strength, min, ksi Yield Strength min, ksi C Elongation in 4D, min, % D
    Alloy Cu 655 F468L All 60-80 HRB 50-80 20 50 15 20
    • (A) Where both tension and hardness tests are performed, the tension tests shall take precedence for acceptance purposes. For aluminum and titanium alloys, hardness tests are for information only. See 6.5.
    • (B) The yield and tensile strength values for full-size products shall be computed by dividing the yield and maximum tensile load by the stress area for the product diameter and thread pitch as given in table on tensile stress areas.
    • (C) Yield strength is the stress at which an offset of 0.2 % gage length occurs.
    • (D) Elongation is determined using a gage length of 4 diameters of test specimen in accordance with Test Methods E8/E8M.
    • (E) "HF" denotes a hot-formed product.
    • (F) Aluminum alloy temper designations are in accordance with ANSI H35.1.
    • (G) Full-size test mechanical properties apply to fasteners with a maximum diameter of 76 mm. Mechanical properties of larger sections shall be negotiated between the material manufacturer and the fastener producer.
    • (H) Ti 5 Class A requires wedge tensile testing in accordance with Ti 5 Class B requires wedge tensile testing in accordance.

    ASTM F468/F468M Grade C65500 655 Silicon Bronze Tensile Stress Areas and Threads(Inch)

    Nominal Size, in. Coarse Threads-UNC Fine Threads-UNF 8 Thread Series-8UN
    Threads/ in. Stress Area A , in. 2 Threads/ in. Stress Area A , in. 2 Threads/ in. Stress Area A , in. 2
    1 / 4 20 0.0318 28 0.0364 . . . . . .
    5 / 16 18 0.0524 24 0.0580 . . . . . .
    3 / 18 16 0.0775 24 0.0878 . . . . . .
    7 / 16 14 0.1063 20 0.1187 . . . . . .
    1 / 2 13 0.1419 20 0.1599 . . . . . .
    9 / 16 12 0.1820 18 0.2030 . . . . . .
    5 / 8 11 0.2260 18 0.2560 . . . . . .
    3 / 4 10 0.3340 16 0.3730 . . . . . .
    7 / 8 9 0.4620 14 0.5090 . . . . . .
    1 8 0.6060 12 0.6630 . . . . . .
    1 1 / 8 7 0.7630 12 0.8560 8 0.790
    1 1 / 4 7 0.9690 12 1.0730 8 1.000
    1 3 / 8 6 1.1550 12 1.3150 8 1.233
    1 1 / 2 6 1.4050 12 1.5810 8 1.492
    • (A) Tensile stress areas are computed using the following formula:
    • A s = 0.7854 [ D - 0.9743/n ]
    • where:
    • As = tensile stress area, in.2,
    • D = nominal size (basic major diameter), in., and
    • n = number of threads per inch.

    ASTM F468/F468M Grade C65500 655 Silicon Bronze Tensile Stress Areas (Metric)

    Nominal Product Diameter and Thread Pitch Stress Area, A mm 2 Nominal Product Diameter and Thread Pitch Stress Area, A mm 2
    M6 × 1 20.1 M16 × 2 157
    M8 × 1.25 36.6 M20 × 2.5 245
    M10 × 1.5 58.0 M24 × 3 353
    M12 × 1.75 84.3 M30 × 3.5 561
    M14 × 2 115 M36 × 4 817
    • (A) Tensile stress areas are computed using the following formula:
    • A s = 0.7854 (D − 0.9382 P) 2
    • where:
    • As = stress area, mm2,
    • D  = nominal thread diameter, mm, and
    • P  = thread pitch, mm.

    Frequently Asked Questions

    What is Silicon Bronze C65500?

    Silicon bronze C65500 is a Cu-Si-Mn alloy (~96 Cu, 3 Si, 1 Mn) per ASTM F468 - the workhorse silicon bronze for bolting + marine + architectural applications. Tensile 55-100 ksi depending on temper. Excellent strength + corrosion resistance + weldability + non-sparking behavior.

    Why is C65500 used in architectural bolting?

    C65500 weathers to a stable brown patina (similar to traditional bronze) without dezincification. Used for exterior architectural fasteners on bronze cladding, statuary mounting bolts, and high-end marine yacht hardware where appearance + corrosion resistance both matter.

    Non-sparking applications?

    C65500 is non-ferrous and does not produce sparks on impact - making it acceptable for bolting in flammable-atmosphere applications (refineries, gas plants, grain elevators) where ferrous bolts would be a safety hazard.

    Available dimensional patterns?

    Full F468 ASME B18 inch + metric range. Highest-volume silicon bronze fastener spec - generally well-stocked.

    References & Standards

    • ASTM F468 / F468M - Standard Specification for Nonferrous Bolts, Hex Cap Screws, and Studs for General Use
    • ASTM F467 / F467M - Companion specification for Nonferrous Nuts (mate with F468 for matched-alloy assemblies)
    • ASTM F436 / F436M - Hardened steel washers (ferrous washer companion when nonferrous washers are not specified)
    • NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum and natural gas industries
    • ASME B18.2.1 / B18.2.3 series / B18.3 / B18.6.7M / B18.31 / B16.5 - Dimensional standards referenced by F468
    • DIN 912 / 933 / 931 - Metric hex socket head and hex head cap screw dimensional standards
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